Elephant seals’ rhythm may make males fight

If you’re a beta northern elephant seal and you hear one sound, you might run.

But when you hear another sound, you might scratch your head and wait to see what happens.

And here’s why: In the rhythm and pitch of the first call, you recognize one voice as a familiar, more dominant male that you have fought with before. But you can’t discern the other, modified call, according to a study published Thursday in Current Biology. This suggests that elephant seals are the only known mammals other than humans that can use rhythm to recognize and respond to other members of their species in the wild.

During breeding season, between December and March, elephant seals take a break from their lives at sea and congregate on the West Coast from San Francisco to Mexico. The males, called bulls, arrive first and fight to establish dominance. Winning males become alphas with a whole harem of females with which they can breed. Losers become betas, connecting with females only opportunistically, when the alphas aren’t around and dominating other males that are even lower in the hierarchy.

What researchers already knew is that as they battle, the male elephant seals call out in rhythmic clicks or grunts that announce their identities. A few clicks may say: “I am Antonio, the Elephant Seal King,” “I am Paul, Prince of the Elephant Seals,” or “Hi, I’m Joe — just an average citizen seal here to learn.”

These voices are always the same, remaining stable year to year. Even young males not yet ready to breed arrive at the colony to start learning its social network. Knowing the ranks of your male colony mates is important for survival, because bulls are big and powerful: They stretch up to 16 feet long, can weigh more than 2 tons and possess toothy mouths with four sharp canines. An easily avoided fight can mean life or death for the seal.

And knowing the ranks comes down to identifying, learning and remembering particular characteristics of individual calls, the French American team of researchers found in its latest study.

“At the very beginning of our elephant seal studies, we thought that males maybe sent information about their physical ability to fight,” said Nicolas Mathevon, a biologist at the University of Lyon/Saint-Etienne in France, who helped lead the study. But “the main call is like a fingerprint” that reveals a seal’s individual identity, not its strength.

At Año Nuevo State Park in Pescadero, the researchers recorded calls from elephant seals up and down the hierarchy. Later, they returned to the beach with calls they had altered in the lab. They set up speakers a foot tall a few yards from the seals and played back the original and modified calls of alpha seals to beta seals.

The team found that the subordinate seals recognized the rhythm and pitch of the original dominant individual’s call and fled. But when the researchers manipulated the original call, sliding the pitch higher or lower or the rhythm faster or slower — by just a little so it still resembled a seal — the subordinate seals reacted to the modified calls just as they would the calls of strangers: They waited to see what type of interaction would follow.

Some animals have been trained to detect rhythms. Palm cockatoos can bang out beats with sticks, and bottlenose dolphins and humpback whales can learn the signature whistles and songs of others. But this is the first study to experimentally demonstrate that a nonhuman mammal can use the rhythm of another’s voice to make decisions that affect survival.